iphone - Xcode unit testing

Question

I have never used Unit Testing and I understand the uses of it but I don't really know when and how to use it.

I would like to know when it's worth it to use Unit Testing, maybe with some examples.

Answer 1

The other answers tell when but not really how, so let me add an answer also.

When

Any time you are writing production code that you are going to keep, you should have Unit Testing for it. The most helpful training that I saw on this was the following 2-part video series:

• Understanding Test Driven Development (part 1)
• Unit Testing Best Practices with Roy Osherove (part 2)

The first five minutes or so are just intro so you can skip to the end of that.

How

I am using Xcode 7 with Swift.

Start a new project and add a Unit Test.

I am calling mine MyProject. If you open the MyProjectTests group in the Project Navigator, you will see that Xcode has already created a Unit Test file for you called MyProjectTest.swift.

You can delete all the example methods for now and add a new func to test your own class method. Be sure to add the line @testable import MyProject at the top. If your project name has spaces in it then replace the spaces with underscores. (For example, "My Example Project" would use @testable import My_Example_Project.)

I am following the naming pattern of testMethodNameBeingTested_Senario_ExpectedBehavior. Unit Test names must begin with "test".

I will do something like this:

import XCTest
@testable import MyProject

class MyProjectTests: XCTestCase {
    
    func testSum_TwoNumbers_ReturnsSum() {
        // Arrange (set up the needed objects)
        let myClass = MyClass()
        
        // Act (run the method you want to test)
        let sum = myClass.sum(1, 2)
        
        // Assert (test that the behavior is as expected)
        XCTAssertEqual(sum, 3)
        
    }
}

Of course, the build fails because we haven't added the MyClass class yet.

Add your class.

I am adding a Swift file to MyProject called MyClass.

class MyClass {
    
    func sum(a: Int, _ b: Int) -> Int {
        return a + b
    }
}

Press the test button next to the Test Unit Class or method to run the test again and it should pass.

To see it fail (an important part of Unit Testing) you could do something like return 0 in the sum method of MyClass. Then you would see the following when you run test:

You can go back and fix this and then add more Unit Tests. You can also make other Unit Test files for different classes if you like. Just right click the MyProjectTest group in the Project Navigator and choose "New File" Then choose Test Case Class.

Related

Xcode UI Test example